Anyone running Redline Heavy shockproof in the differential

[Dogariffic]

I have read that it can quite things down a bit.

My son picked up a 1978 280Z with about 115k miles. Hardly driven at all the past 20 years....A little rust but manageable.  He and I are working on it together.

Did a search and did not see this product discussed.  Planning to put Redline MT 90 in the transmission, but looking for recommendations...and one of the Redline Shockproofs in the differential, but would consider other options.  Things work ok but am trying to quiet things down a bit (gear noise)....Noise travels I know and replacing rear bushings (Mustache is done) and bearings are next.

And I have the FSM by the way...

Thanks in advance.

[heyitsrama]

Some members like AC Delco Friction Modified trans oil, but I'm unsure if it could also be applied to the diff. I don't see why not.

[S30Driver]

Use the Delco Friction Modified in the transmission - superior to the Redline for this purpose.   Redline 75w90 for the rear diff.

[Zed Head]

4 minutes ago, S30Driver said:

Use the Delco Friction Modified in the transmission - superior to the Redline for this purpose.  

How do you know?  Curious.  I know that people like both but haven't seen the one-to-one comparison results.

Diff noise in the cabin is usually caused by the way the diff is mounted.  The diffs are inherently noisy.  You need to get the bushings right to quiet things down.

[Chickenman]

No, you cannot used the AC Delco FM transmission oil in the diff ( or any other GL4 transmission oils ) . It does not have the high pressure additives necessary for Hypoid gears. Totally different formulations for totally different gear loadings. Hypoid diffs require GL5 with extreme pressure additives. From personal use I would highly recommend the AC Delco Friction Modified transmission oil though. The stuff is magic.

These cars don't have a lot of sound insulation and even the slightest gear whine is amplified by the hatch area,  I would consider ling the whole hatch floor with Dynamat ( or a similar product ) to dampen the noise. Will help with road noise as well. 240Z's are particularly bad as they have next to nothing for sound insulation. 

Getting back your original question. It really depends on how bad the gear whine is.  I've been considering the same thing. I have a slight gear whine the R200 of my 280Z. Just enough to be annoying. Could also be a pinion bearing whine, but I digress. I'm using a 80w/90 ( Amsoil ) and am considering going to a 80w/110 ( one of the new mid-weights). I know some of the local 510 guys have used RL shockproof oil in their diffs and it does quiet them down some. The Lightweight shock proof oil should be enough. If you have to use the Heavy Weight stuff, you have something mechanically wrong.

One thing to consider, is that after sitting for 20 yaers with out moving, you may have some corrosion damage to the diff bearings. In fact I'd be surprised if you didn't. Moisture will accumulate after all those years via condensation. That will produce acids in the diff oil which will cause etching on the roller bearings. Might be an idea to tear it down and inspect or replace all the bearings as insurance. 

 

[S30Driver]

I know from 1st hand experience, plus I remember Zup replaced his Redline filled tranny with Delco and reported a very noticeable improvement in shifting - especially when cold.   Redline is a good product, but in the case of the transmission, the AC Delco product is better.

[Zed Head]

So cold weather shifting is the improvement?  Notchiness?  For Zup.  What was your experience?

I don't want to badger you but I always like to see the data.  You made a firm statement of superiority but it's not clear what, exactly, is better about it..  There are so many different qualities to transmission performance that they need to be defined before you can say better or worse.

[Chickenman]

3 minutes ago, Zed Head said:

How do you know?  Curious.  I know that people like both but haven't seen the one-to-one comparison results.

Diff noise in the cabin is usually caused by the way the diff is mounted.  The diffs are inherently noisy.  You need to get the bushings right to quiet things down.

Anecdotal evidence . There are enough people on Suby, Honda, VW/Audi, Toyota and Nissan forums that have reported great success with the AC Delco over Redline, that it supports the premise. Also when your local GM  Parts Managers tell you  they  are selling large quantities of this product to Honda, Nissan, Toyota, BMW and other dealerships in large volumes to fix " problem " cars... it adds to the credibility. Our local Jobber suppliers ( Lordco, NAPA etc ) also report the same thing. Big demand for this stuff to improve shift quality in non-GM cars. We have a lot of 510 owners in BC, and they are also reporting great success with the GM product over RL and other brands. And it's on the Internet so it must be true...

 I don't think you're ever going to get someone to provide Lab results with measured sound and vibration levels, so " in the field results "  are all we can go by. I've personally used both the Redline MT. Amsoil MT and AC Delco FM oils in my Audi. The AC Delco oil definitely worked much better than the RL or Amsoil and saved me from having to do a rebuild due to a damaged 2nd gear synchro. It makes sense as the GM oil was originally made to correct a scratchy shift problem on Gertrag gear boxes ( Brass synchros ) on the Cobalt SS and Soltice . It is a GL-S ( " S " for SAM ) formulation. The " S " stands for " special " or proprietary formulations that are above and beyond of the normal API GL-4 and GL-5 classifications. Many manufacturers have special formulations for there transmissions and diffs these days. Especially European cars. 

The diff noise is certainly a part of Cabin design. Only so much you can do to eliminate it. 

 

[Zed Head]

I'd bet you'll find just as many anecdotes about Redline.  I have one myself, but it's specific to a certain problem.

I just like a good solid decisive-making process, not 2nd hand, I know somebody stories.  They're a good starting point but not something that should be used to make a firm statement.

I don't even use Redline so don't have a dog here.  Just talking about the process.

[Chickenman]

Regarding ZH's question. For me it was the improvement in shift quality. Especially in cold wheather but also when warm. Eliminated baulky or notchy shifting. When warm the transmissions on both cars just fall into gear like a hot knife through butter. And cold weather notchiness is greatly reduced. It works on modern transmissions as well, as a friend of mine tried it on his 2006 Infinity G35. He always had a slightly notchy shift quality and he's tried several different oils including the RL MT. The AC Delco FM oil totally eliminated any notchy shifting. He's gone on G35 and G37 forums and had feedback that other owners had the same experience. 510 Realm owners up in the Great White North are also reporting improved shift quality in colder weather. Below 50F seems to be the area where you see the main  improvement in shift quality.

I think some of the results tend to be regional. Cold climates ( such as Canada ) tend to have more issues with notchy shifting than warmer climates in the South. Could be the reason why our local GM dealers in BC sell so much of it. Notchy shifting when cold may not be an issue California, Florida or Texas for example. BC is fairly mild compared to the rest of Canada, so back East and on the Prairies may have even better results. All I know is that the stuff works in our Climate.  

[Chickenman]

3 minutes ago, Zed Head said:

I'd bet you'll find just as many anecdotes about Redline.  I have one myself, but it's specific to a certain problem.

I just like a good solid decisive-making process, not 2nd hand, I know somebody stories.  They're a good starting point but not something that should be used to make a firm statement.

I don't even use Redline so don't have a dog here.  Just talking about the process.

Here's the thing about that line of reasoning. Now I've never seen an live Alligator in my life. Now if I went to Florida and a resident ( maybe Troy Landry ) pointed out a gator and told me " Watch it. Those things are dangerous. They'll kill you in a second".  Now, I'm gonna tend to go with his anecdotal and real life  experience. I'm not about to say. " Well, I'm going to ignore all that you've told me because you don't have any factual data to present and back up your statement ".  

In my world, real life experiences and in field results hold equal weight in as hard core Data . So far I haven't been eaten by a Gator.....

 

[Zed Head]

28 minutes ago, Chickenman said:

Here's the thing about that line of reasoning. Now I've never seen an live Alligator in my life. Now if I went to Florida and a resident ( maybe Troy Landry ) pointed out a gator and told me " Watch it. Those things are dangerous. They'll kill you in a second".  Now, I'm gonna tend to go with his anecdotal and real life  experience. I'm not about to say. " Well, I'm going to ignore all that you've told me because you don't have any factual data to present and back up your statement ".  

In my world, real life experiences and in field results hold equal weight in as hard core Data . So far I haven't been eaten by a Gator.....

 

You've kind of come over to my side and are rephrasing what I said.  Field results are data, the more specific the better.  Anecdotes about "my buddy tried it and said it's "better" are 2nd hand stories, vaguely told.  No offense to anyone who'd done that, but there's a principle called "cognitive bias" that describes how people generally think that that what they're doing or using is better.  They see what they want to see.  That's why we measure things and put numbers on them if we can.